1982年 · 第02卷第02期

Authors made a survey of inhabitants' tissue-absorbed doses arising from inhalation of ²²²Rn, ²²⁰Rn and their short-lived decay products in the high background radiation area in Yangjiang County, and in the neighboring control area in Enping and Taishan Counties as well; all of these counties are located in Guangdong Province, China. The methods of rational distribution of samples and measurement, the calculations of average precision of measurement and tissue doses are discussed. A two-filter method is used for measuremente of ²²²Rn and ²²⁰Rn in air. The concentration of short-lived decay products of ²²²Rn and ²²⁰Rn in air are calculated from five timeintervals α counts on a sampling filter.

The average concentrations of ²²⁰Rn in air of the high background radiation area indoors and outdoors are 4.526 and 0.498pCil^-1 respectively, which are equal to 9.6 and 4.8 times the concentrations of the control area. The average concentrations of ²²²Rn in air of the high background area indoors and outdoors are 0.929 and 0.441pCil^-1, corresponding to 3.3 and 1.4 times of the control area respectively. The average Working Levels of radon daughters and thoron daughters in the high background area are 0.00462 and 0.01312 (indoors), and 0.00435 and 0.00230 (outdoors), corresponding to 3.6 and 4.9 times (indoors), and 2.7 and 4.5 times (outdoors) respectively.

The annual tissue absorbed doses ariings from inhalation of ²²²Rn, ²²⁰Rn and their decay products in high background radiaton area are estimated to be 328.85 mrad in the segmental bronchioles, 65.77 mrad in the whole lung, 0.32 mrad in the gonads and 1.26 mrad in the bone marrow and bone lining cells. These results are 3.2~4.2 times that in the neighboring control area.

Using the determination method for radon in breath, we have investigated the radium body contents of the inhabitants, who were 19 to 30 years old, living in the high background and control areas respectively (20 people in each area, male : female=1: 1). From this survey it was estimated that the average radium body content for the inhabitants in the high background area is about 12.0×10^-4 µCi, and that for the inhabitants in the control area is about 2.4×10^-4µCi. The ratio of the former to latter is 5 : 1. This value is very close to the ratio between the radium contents in surface soil of these two areas, which is 4.8 : 1. It shows that the radium in soil transfers through the food chain in the same proportion into human body. In addition, we have evaluated the average annual doses absorbed by endosteum and red bone marrow of the inhabitants in both areas.

This paper reports the concentrations of U, Th, ²²⁶Ra ⁴⁰K radionuclides in 60 soil samples of both the high background and the control areas. Results show that the data obtained by radiochemical methods are consistent with those by gamma spectrometry.